Formation of volatile compounds and brown products in the model system n-hexanal-glycine

During the boiling of a mixture of n-hexanal and glycine in aqueous medium, pH value 9, both soluble and insoluble brown colored pigments and volatile compounds were formed. The following volatile compounds were identified by gas chromatography and mass spectrometry; hexanone, decenone, undecenone, undecan-5-one, undecenedione, dodecenone, tridecanone, dodecanedione, tridecenone, dodecenedione, hexenyl hexanoate, caproic, valeric and butyric acids. The brown coloured pigments insoluble in water contained 0.57% of nitrogen. The presence of conjugated double-bonds, carbonyl and carboxyl groups was confirmed by spectral methods. The pigments were also separated by thin-layer chromatography on silica gel.